Assessing 'coastal squeeze' of wetlands at the Yellow River Delta in China: A case study

Coastal wetlands worldwide are subject to increasing threats from continued sea level rise (SLR), while their potential adaptation through land-ward migration is often impeded by natural or man-made barriers. The resultant sea- and land-ward squeeze exacerbates the loss of wetlands, causing severe ecological consequences. To address this issue for coastal wetlands at the Yellow River Delta (YRD) in China, the present study adapted a fuzzy-system-model (FSM) based coastal squeeze assessment method (Torio and Chmura, 2013) to assess the potential of coastal squeeze under assumed future SLR scenarios. Coastal squeeze indices for slope and surface imperviousness were integrated to generate the composite coastal squeeze index (CCSI) as a unified metric that accounts for both factors as the primary contributors to coastal squeeze. The distribution of the confidence weighted CCSI was used to identify vulnerable area at three selected study sites, and results for three representative years, i.e., 1989, 2000 and 2010, were compared to illustrate the historical changes in recent decades. Due to the predominately flat topography at the YRD, slope was found to be an insignificant contributor to coastal squeeze, whereas surface imperviousness plays a dominant role. As such, the coastal squeeze potentials at the three study sites in 2000 appeared to be considerably higher than those at 1989 and 2010 as the surface imperviousness experienced increasing-then-decreasing variation arising from concurrent land cover change. The average coastal squeeze potential at the three study sites in 2000 also tended to be more sensitive to the assumed SLR scenarios, and featured a prominent peak at 1.5 m SLR. The present study showcases the assessment of coastal squeeze of wetlands at the YRD and the region, and provides important references for coastal wetland conservation efforts under increasing threats from climate change and human activities.